Overrating rhymes with:
berating, crating, grating, rating, abating, annotating, awaiting, baiting, berating, crating, creating, dating, debating, deflating, elating, equating, gating, grating, hating, inflating, innovating, mating, misstating, negating, plaiting, plating, postdating, procreating, rating, reinstating, relating, restating, sedating, skating, slating, stating, translating, updating, waiting, weighting
Overrating sounds like:
operating, operation's, operations, operations', overdoing, overeating, overheating, overriding, overtones, overwriting